If your refrigerator suddenly stopped freezing or makes unusual sounds, the first thing that comes to mind is a problem with the motor. It is this unit that is the “heart” of the cooling system, ensuring the circulation of refrigerant through the tubes. Understanding what's inside the motor helps owners better diagnose problems and make informed decisions about repairing or replacing expensive equipment.
The internal structure of a compressor is a complex mechanism that operates under high pressure. Many people mistakenly believe that there is only an electric motor inside, but the actual design includes a piston group, valves, a lubrication system and complex electronics. Let's look in detail at what this sealed unit consists of.
Compressor design: sealed casing
Externally, the motor is a black or gray metal cylinder, located, as a rule, in the lower rear part of the refrigerator. This housing is called a casing, and it is completely sealed Welded casing necessary to contain the refrigerant and high-pressure oil vapors inside, preventing them from leaking into the atmosphere. Inside this “boiler” there is a specific environment, saturated with freon and oil vapors.
Inside the casing, the compressor unit itself is suspended on four springs. This damping system is critical because it dampens the vibrations that occur when the pistons operate. If the springs break or jump off, you will hear a loud metallic clang and knock when starting the equipment. Inverter models They may have a slightly different suspension system, but the principle of vibration damping remains the same.
The casing also serves as a heat exchanger. During operation, the unit becomes very hot, and the metal surface dissipates heat into the surrounding space. That is why it is not recommended to touch a running motor with your hands - the surface temperature can reach 80-90 degrees Celsius.
⚠️ Attention! Never attempt to open a sealed compressor casing yourself without special equipment and skills. Inside there is oil mixed with freon, and residual pressure may also remain. Opening it at home is dangerous and makes further operation of the unit impossible without professional refilling and soldering.
Electrical part: stator, rotor and start relay
The basis of the internal mechanism is an electric motor that drives the piston group. It consists of two main elements: a stationary stator and a rotating rotor. Stator is a set of metal plates with wound copper wire (windings). In classic models there are two of them: starting and working.
The rotor, or armature, is inserted inside the stator and rigidly fixed to the crankshaft. When electric current is applied, a magnetic field is created in the windings, which causes the rotor to rotate. In modern inverter compressors the design may be different: they use frequency control, which allows you to smoothly change the rotation speed, which makes the operation quieter and more economical.
An external but critical element is responsible for starting the engine - the starting relay. It is attached directly to the terminals of the motor windings. The relay sends a powerful impulse to the starting winding to move the rotor. As soon as the shaft picks up speed, the relay turns off the starting winding. If this element is faulty, the motor will hum, but will not start.
Mechanical part: pistons, cylinders and valves
The heart of the mechanics is the crank mechanism, hidden in the lower part of the internal block. The crankshaft, rotating, converts the rotational movement of the rotor into the translational movement of the pistons. The pistons, in turn, compress the freon gas coming from the evaporator and push it into the condenser under high pressure.
Gas compression occurs in the cylinders. Special plate valves are installed at the ends of the cylinders. Suction valve passes gas inside the cylinder, and the discharge valve releases it outside. These thin metal plates operate at tremendous speed and frequency. Their wear or breakdown leads to a drop in compressor performance: the motor works, but there is no cold.
All these mechanics require constant lubrication. In the lower part of the casing there is oil, which is sprayed by rotating parts or supplied through the shaft channels under pressure. Lack of oil or its low level is the main reason for piston jamming and engine failure. Oil also helps remove heat from rubbing parts.
| Component | Function | Symptoms of malfunction |
|---|---|---|
| Piston group | Refrigerant compression | No cold, quiet operation |
| Start relay | Starting the engine | Clicks, humming without starting |
| Stator windings | Creating a magnetic field | Knocking out plugs, burning smell |
| Valve plates | Gas flow control | Reduced cooling efficiency |
Why are compressors called hermetic?
Tightness is necessary to preserve the properties of the refrigerant and oils Unlike open compressors in industry, household models do not have shaft seals, since any gap would lead to rapid leakage of freon and moisture entering the system.
Types of compressors: linear and inverter
Technologies do not stand still, and the internal structure of motors is evolving. Traditional compressors operate on a start-stop principle: they turn on at full power, cool the chamber to a set temperature and turn off. Then the cycle repeats. This creates temperature differences and increased wear of the mechanics during startup.
Inverter motors are free of this drawback. A control board is installed inside them, which converts alternating current into direct current and vice versa, allowing you to smoothly regulate the speed of rotation of the shaft. Such a motor does not turn off completely, but only slows down to maintain the temperature. This ensures less noise and energy consumption.
Linear compressors, often found in technology LG, have an even simpler design. They do not have a rotating shaft or crank mechanism. The piston moves back and forth due to electromagnetic forces. The absence of rubbing rotating parts makes them very quiet and durable, but sensitive to power surges in the network.
☑️ Motor diagnostics
Typical malfunctions of the internal part
The most common problem that owners encounter is interturn short circuit of the windings. This occurs when the insulation of the stator copper wire deteriorates due to overheating or age. As a result, the engine begins to consume current higher than the rated one, hum strongly and heat up quickly. Thermal relay in such cases it is triggered, opening the circuit to prevent a fire.
The second common problem is jamming of the mechanical part. This can happen due to oil burnout, moisture entering the system (which leads to acid formation and corrosion), or destruction of piston parts. The motor hums, trying to turn over, but the shaft stands still. In this case, a short-term supply of increased voltage (professional procedure) often helps, but often the unit requires replacement.
The third problem is an open circuit. The wire may burn out inside the winding or burn out at the soldering point. In this case, the motor is silent and does not respond when turned on. Diagnostics shows infinite resistance between the contacts.
⚠️ Attention! If you smell burning insulation or see sparking in the motor area, immediately unplug the refrigerator. Operation with damaged electrical wiring can lead to a fire in the plastic elements of the refrigerator.
Diagnostics and replacement: is it worth repairing?
Repairing the insides of the compressor in domestic conditions is impossible. Even if you find the reason (for example, stuck valves), it is almost impossible to disassemble and, most importantly, weld the casing back without losing the tightness and properties of the metal. Therefore, repairs usually involve a complete replacement of the complete unit.
For diagnostics, the technician uses a multimeter. It “rings” three contacts on the motor (common, starting, working). The normal resistance of the working winding is usually 10-30 Ohms, the starting winding is 20-50 Ohms. The resistance between the case and any contact must be infinite (breakdown test). The starting relay is also checked “by ear” (the ball must move freely) and with a tester.
Replacing a motor is a labor-intensive process. It requires:
- ⚙️ Pumping out residual freon from the system.
- 🔥 Dismantling the old compressor (cutting pipes).
- 🔧 Installing a new unit and soldering connections.
- ❄️ Evacuate the system and charge it with new refrigerant.
The cost of replacement is often a significant part of the price of a new refrigerator. If the equipment is less than 5-7 years old, replacing the motor is justified. If the refrigerator is old, it is more economically feasible to purchase a new model with a modern energy efficiency class.
Why is the refrigerator motor hot?
The normal operating temperature of the compressor casing can reach 90 degrees Celsius. This is due to the fact that gas compression occurs inside, which, according to the laws of physics, is always accompanied by heating. If the engine is hot, but the refrigerator is freezing, this is normal. You should sound the alarm if it is red-hot or smells of burnt wiring.
Is it possible to lubricate the refrigerator motor?
No, you cannot. Inside the casing there is a special synthetic or mineral oil designed to work with freon. Adding third-party oils (for example, WD-40 or machine oil) through the tubes will lead to a chemical reaction, the formation of acids and complete failure of the system.
How long does a compressor last?
The average service life of modern compressors is 10-15 years. Inverter models can operate longer due to the absence of constant starting loads. The service life strongly depends on operating conditions: room temperature, voltage stability and defrosting frequency.
What to do if the motor hums but does not start?
First, unplug the refrigerator for 1-2 hours. If after turning it on it starts, the problem was with the thermal relay or overheating. If the humming repeats and after a while a shutdown click is heard, the start relay is most likely faulty or the compressor is jammed. A specialist diagnosis is required.